THE POTENTIAL OF MAWRTH VALLIS AS A BIOLOGICALLY ROBUST PALEOENVIRONMENT AND PRIME CANDIDATE TO PRESERVE BIOMARKERS – SUPPORT FOR MSL LANDING SITE SELECTION

Utilizing THEMIS and HiRISE visual data, several light-toned, apparently sedimentary, layers have been identified in the Mawrth Vallis region of Mars, near a proposed landing site for the Mars Science Laboratory (MSL) (24.65°N, 340.1°E). Analysis of data collected by the OMEGA, CRISM, and GRS instruments indicates that these layers contain abundant smectite clays. Formation of smectite clays is commonly associated with prolonged hydration and a neutral to slightly alkaline pH environment suitable to many terrestrial organisms. The favored interpretation of these light-toned units as Noachian-aged fluvial/marine deposits yielding abundant smectite clays is congruent with terrestrial analogs as an area highly likely to have provided a habitat for organisms living on Mars, if ever they existed, at a time when such an environment was most probable. Additionally, the sedimentation and rapid burial occurring within these environments would provide an excellent mechanism for the preservation of organisms. Polygonal “mud cracks” observed within the light-toned layers suggest a rapid removal of fluid from the system, further increasing the likelihood of preservation of buried organisms. A discontinuous, overlying dark unit suggests that these ancient layers have only recently been exhumed through erosion, revealing fresh, relatively unaltered bedrock. The light-toned outcrops near Mawrth Vallis provide an easily accessible location where perhaps the greatest potential for direct evidence of past life on Mars exists. Here, NASA's planned MSL lander would be capable of returning images of this evidence to Earth, while simultaneously fulfilling other goals of the mission such as constraining geology, climate, and surface radiation.